Effect of different healing stages on stable isotope ratios in skeletal lesions.

INTRODUCTION

Physiological stress is one of the various factors that can have an impact on stable isotope ratios. However, its effect on bone collagen stable isotope ratios is still not fully understood. This study aims to build on previous research on how different disease stages may affect bone collagen stable isotope ratios.

MATERIALS AND METHODS

Carbon (δ C) and nitrogen (δ N) isotope ratios were assessed in 33 skeletons that retained evidence of infectious disease and healed fractures. Samples were taken from active lesions (long bones n = 14; ribs n = 4), healed lesions (long bones n = 10; ribs n = 9), or a fracture callus (long bones n = 9; ribs n = 3). Results were compared to stable isotope ratios calculated for regions on these bones that did not retain evidence of disease or fracture.

RESULTS

Long bones with active lesions had a significantly higher average δ N (δ N = 11.1 ± 0.9‰) compared to those without lesions (δ N = 10.7 ± 0.7‰; p = .02), while fracture calluses showed the largest range for both δ N and δ C. There were no significant differences in stable isotope ratios when compared between nonlesion and lesion sites in the ribs.

DISCUSSION

The increase in δ N seen in active lesions, when compared with δ N from nonlesion regions on the same long bone, may be a consequence of altered protein metabolism. The high variability of δ N and δ C in fractures may be related to different healing stages of the calluses. This study suggests that stable isotope data can contribute information about diseases in the past, as well as an individual's response to diseases in the absence of modern medicine and antibiotics.